The manufacture and use of poly (butylene terephthalate) (PBT) polymer containing glass fiber as a reinforcing filler is well known and is described for instance in U.S. Pat. No. 3,814,725. Such reinforced polymers are widely used as molding resins for making various products. While the impact resistance of products molded from glass reinforced PBT is significantly better than that of many products made from other molding compositions, further improvement is desirable.